Optical fibers are widely use as a signal transmission media. Their popularity stems from their small size and from their large bandwidth capability, which is orders of magnitude greater than electrical conductors However, optical fibers are mechanically fragile and exhibit low strain fracture resistances under tensile loading. In addition, optical fibers cannot be sharply bent. This is because the propagation of light through optical fibers can be seriously degraded by too sharp a bend, and the fiber itself can be fractured by such a bend. The fibers, when assembled into a cable, must be capable of withstanding tensile loads and binding stresses caused when the cable is pulled along its routing and through turns.
Typically, optical fibers are produced and bonded together so as to provide a fiber array or ribbon containing multiple fibers. The ribbon may have any number of fibers, but the fibers are commonly assembled in a co-planar array having four, six, eight, twelve, sixteen, or twenty-four fibers, with a twelve fiber ribbon currently being most prevalent. As the use of such ribbons increases, the number of fibers in the array is also expected to increase, and cables or ribbons with hundreds or thousands of individual optical fibers are possible and even likely to appear in the future. Such ribbons and a method of producing them are described, respectively, in U.S. Pat. No. 4,900,126 to Jackson et al. and U.S. Pat. Nos. 4,980,007 and 5,076,881, both to Ferguson. These patents, of common assignee, and a paper entitled A Modular Ribbon Design For Increased Packing Density Of Fiber Optic Cables, by Jackson et al., are incorporated herein by reference.
As discussed in the above-mentioned references, the multiple optical fibers are typically color-coded and held together by a cladding, or matrix, which secures the fibers in the desired array. The fibers may, however, be easily separated, singly or in groups, as the modulus of the cladding or bonding material is such that interfiber movement is allowed. The fibers can be accessed individually, yet the bonding material provides suitable mechanical properties for the entire array such that the ribbon maintains its bonded state absent a positive attempt to separate fibers from the ribbon.
Methods for separating individual fibers from the array vary, with one method, that of Jackson et al. in U.S. Pat. No. 4,900,126, being described as the application of peeling forces by a craftsperson. While this is easily accomplished when dealing with the end of a ribbon, such an operation is considerably more difficult if the ribbon must be separated at some point between its ends, to cull out one or more fibers for routing elsewhere. Razor blades or knives have been used in the past for this purpose. However, these devices generally lack the required precision when dealing with the close tolerances of the ribbons. Since some or all of the fibers in the ribbon may be in use, or "live", it is extremely important that the fibers not be nicked or cut during separation, which would result in a diminished or total loss of signal.
Another method used for separating individual fibers from the ribbon employs the use of chemical means. Soaking the ribbon in alcohol or another suitable solution can dissolve the matrix or bonding material which secures the fibers together in an array. One particularly disadvantageous result is that the dissolution of the bonding material separates all of the fibers. While individual fibers may now be selected out and routed elsewhere, the separated fibers in the ribbon must then be resecured to ensure the integrity of the remaining fibers. Such resecurement can be unwieldy, at best, and at worst, impossible, depending on the location of the ribbon and/or its environment. In addition, depending on the location of the ribbon and/or the composition of the bonding material holding the fibers together, chemical methods of separation may not be possible or may be hazardous to the ribbon, the serviced equipment, or the technician.
Accordingly, a need exists for a method and apparatus for mechanically separating individual fibers or groups of fibers from a multi-fiber ribbon which is quick and easy to apply and which prevents the fibers from being damaged as they are being separated.